Friday, January 26, 2007

Why Do Men Have Nipples?

I woke early from a sweet, now-unremembered dream with a question pulsating in my mind. Why do we have nipples - we, meaning men? I've been focusing on my own man tits for the past several months now because - well, I'll get to that later. But why nips? I decided to do some research. What I've found might surprise you.

So I repeat my question, "Why do men have nipples?"

To tell you the truth, nobody really knows. The best explanation I've been able to find (and frankly it doesn't explain very much) is that nipples aren't a sex-linked characteristic. In other words, nipples are just one of those sexually neutral pieces of equipment, like arms or brains, that humans get regardless of sex.

As you may know, every human being gets a unique set of 23 pairs of chromosomes at conception. These fall into two categories. One pair of chromosomes determines sex--the XX combination means you become female, the XY combination means you become male.

The other 22 pairs, the non-sex chromosomes (they're called autosomes), supply what we might call the standard equipment that all humans get. These 22 pairs constitute an all-purpose genetic blueprint that in effect is programmed for either maleness or femaleness by the sex chromosomes. The programming is done by the hormones secreted by the sex glands.

For example, the autosomes give you a voice box, while the sex hormones determine whether it's going to be a deep male voice or a high female voice. Similarly, the autosomes give you nipples, and the sex hormones determine whether said nipples are going to be functioning (in females) or not (in males).

One interesting consequence of the developmental set-up just described is that during the very early stages of fetal life, before the sex hormones have had a chance to do their stuff, all humans are basically bisexual. Among other things, you have two sets of primitive plumbing--one male, one female. Only one set develops into a mature urogenital system, but you retain traces of the other for the rest of your life.

Men and women are mammals (from the Latin, mamma breast) a species that [has] breasts and feeds its young with milk. The human embryo has tissue that will evolve into breasts. Both male and female babies are born with nipples and ducts intact. It is the presence of genes that direct hormones to differentiate the breast tissue. The Y chromosome stimulates hormones such as testosterone to form male features.

In a now-famous paper, Stephen Jay Gould and Richard C. Lewontin emphasize that we should not immediately assume that every trait has an adaptive explanation. Just as the spandrels of St. Mark's domed cathedral in Venice are simply an architectural consequence of the meeting of a vaulted ceiling with its supporting pillars, the presence of nipples in male mammals is a genetic architectural by-product of nipples in females. So, why do men have nipples? Because females do.

I think that, because we are men, and thus inalienably entitled to any and all pleasures available to the male body, we have nipples so that we can play with them and feel good. There are even classes of men - those who meet with others of their ilk in locations too frightening to the timid - who have replaced the traditional handshake with the nipple tweak. This expresses camaraderie, a willingness to extend pleasure, and a certain level of prurient interest. As for me, plucking my nipples is like flipping a switch. I've often had to alert certain unsuspecting buds of mine to the potential outcome of their actions. Fortunately, this hasn't stopped all of them.